1. Field
Aspects of embodiments of the present invention relate to an energy storage system and a method for driving the same.
2. Description of the Related Art
As environmental disruption, resource depletion, etc., are problematic, interest in a system capable of storing energy and efficiently using the stored energy is increasing. In addition to the system, the importance of renewable energy is increasing. Here, the renewable energy does not cause or hardly causes pollution in a power generation process. An energy storage system is a system that couples renewable energy, a battery system for storing power, and existing grids. The energy storage system stores power produced from the renewable energy in a battery system, and the power stored in the battery system is supplied to a load when the power of a grid is insufficient.
The energy storage system includes a battery system and a power conversion system. The battery system includes a battery and a battery management system. The power conversion system controls the power supply of the renewable energy, the battery system, and the grid.
More specifically, the power conversion system supplies alternating discharge current of the battery and having a predetermined frequency to the battery management system. The battery management system measures the discharge current of the battery, input from the power conversion system, and calculates state of charge (SOC) and state of health (SOH) of the battery using the measured current value. The battery management system outputs, to the power conversion system, data including information on the SOC and SOH of the battery, and the power conversion system charges and discharges the battery based on the SOC and SOH information.
FIG. 1 is a waveform diagram showing measurement times of alternating discharge current generated with a predetermined frequency according to the related art. Referring to FIG. 1, the battery management system receives the alternating discharge current of the battery, generated at a predetermined frequency, from the power conversion system. In FIG. 1, it has been illustrated that the frequency of the discharge current is 100 Hz (hertz); that is, the cycle of the alternating discharge current is 10 ms (milliseconds).
The related art battery management system measures discharge current at predetermined measurement times, such as regular intervals. For example, the related art battery management system measures discharge current every 3 ms (starting from the left) as shown in FIG. 1. The alternating discharge current shown in FIG. 1 is 10 A (amperes), but the discharge current measured by the battery management system is calculated as (10 A+17 A+8 A+8 A)/4=10.75 A. That is, there is a problem in that a deviation or error occurs in the discharge current measured by the related art battery management system. Accordingly, in order to prevent such a measurement error of the discharge current, related art methods such as measuring a frequency of the alternating discharge current of the power conversion system and then directly setting measurement times of discharge current of the battery management system are used.